1. Field
The present application relates generally to wireless communications, and more specifically to methods and systems for handing off an access terminal to a femto access point.
2. Background
Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, 3GPP Long Term Evolution (LTE) systems, and Orthogonal Frequency Division Multiple Access (OFDMA) systems.
Generally, a wireless multiple-access communication system may simultaneously support communication for multiple wireless terminals. Each terminal may communicate with one or more base stations via transmissions on the forward and reverse links. The forward link (or downlink) refers to the communication link from the base stations to the terminals, and the reverse link (or uplink) refers to the communication link from the terminals to the base stations. This communication link may be established via a single-in-single-out, multiple-in-single-out or a Multiple-In-Multiple-Out (MIMO) system.
A new class of small base stations has emerged, which may be installed in a user's home and provide indoor wireless coverage to mobile units using existing broadband Internet connections. Such a base station is generally known as an Access Point (AP) base station, but may also be referred to as Home Node B (HNB) unit, Home evolved Node B unit (HeNB), femto cell, femto Base Station (fBS), base station, or base station transceiver system. Typically, the AP base station is connected to the Internet and the mobile operator's network via a Digital Subscriber Line (DSL), cable internet access, T1/T3, or the like, and offers typical base station functionality, such as Base Transceiver Station (BTS) technology, radio network controller, and gateway support node services. This allows an Access Terminal (AT), also referred to as a cellular/mobile device or handset, or User Equipment (UE), to connect to the AP base station and utilize the wireless service. ATs can include, for example, cellular phones, smart phones, laptops, handheld communication devices, handheld computing devices, satellite radios, navigational devices, Personal Digital Assistants (PDAs), or any other suitable device for communicating over a wireless communication system.
In a heterogeneous wireless access environment that includes both macro base stations and femto base stations, it is imperative that ATs are handed off from macro base stations to femto base stations in a seamless manner. However, scalability issues arise when there is mass deployment of femto AP base stations in a given area. In addition, femto cell pilot pseudo-noise offset ambiguity issues arise during macro to femto handoffs when the AT is in active mode. Accordingly, there is a need for an improved method and system for active handoff of an AT from a macro base station to AP base station that optimizes resource utilization and the end-user experience.